This invention relates to the preparation of an expanded edible protein product which can be utilized in a variety of food products for human and animal consumption. More particularly, the invention relates to heat-processing and working a mix containing a proteinaceous material and a sulfur-containing organic compound and subsequently extruding the mix to produce an expanded protein product having unique physical properties and adaptable for utilization in a wide variety of edible products.
There is a major effort in the world today to produce nutritious, low cost, high protein content meat substitute products. The need for such products which are sought for animal as well as human consumption is wide-spread. A significant effort has been directed toward the utilization of protein flours and meals derived from fish and vegetable seeds, particularly oil seeds such as soy bean, peanut, cottonseed, and the like, to obtain products having desired meat-like texture, consistency, appearance and taste and optimum nutritional values.
British Patent Specification No. 1,049,848, complete specification published Nov. 30, 1966, describes a meat-like product obtained by extrusion-expansion of a protein material derived from vegetable, fish and similar sources via extrusion. The meat-like product is defined as having a plexilamellar structure and as being characterized by an open cell structure in which a majority of the cells have a length to diameter ratio of greater than one, the length being measured in the direction of extrusion and the diameter being measured in the transverse direction. The product, while described as being an expanded product, is found, however, to be very limited in its degree of expansion. Indeed, it is observed that the process there described tends to result in a rather dense product.
More recently, in Australian Patent Specification 15,030/66, laid open to public inspection on June 13, 1968, the preparation of a fibrous porous food product from a protein-containing vegetable material employing an extruder to process a heated, pressurized, mechanically worked mixture of the material is described. The specification further mentions that the addition of a minute amount of elemental sulfur, potassium sulfide or sodium sulfide to the mixture prior to extrusion results in advantageous physical characteristics in the fibrous product.
As indicated above, the expanded protein-containing product described in the British specification tends to be rather dense. On the other hand, the fibrous food product described in the Australian specification, while of a lower density generally, may have residual amounts of sulfur or sulfides present which can produce sometimes detectable off-tastes in the resultant product.
The present invention is directed toward overcoming the disadvantages apparent in the products disclosed in the above-referred-to British and Australian specifications. Other advantages of this invention may be seen from the description which follows.